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Table 3 Testing of Prentice’s criteria three and four for the potential surrogate endpoints for 5-year OSa

From: Identification of surrogate endpoints in patients with locoregionally advanced nasopharyngeal carcinoma receiving neoadjuvant chemotherapy plus concurrent chemoradiotherapy versus concurrent chemoradiotherapy alone

Prentice’s criteria HR (95 % CI)c P-value*
Prentice’s criterion three: Is the surrogate endpoint prognostic for 5-year OS?
 Failure or death from any cause ≤ 3 yearsb 39.0 (16.5–92.3) <0.001
 Failure at any site ≤ 3 yearsb 14.9 (7.9–28.1) <0.001
 Distant metastasis ≤ 3 yearsb 18.1 (9.7–33.8) <0.001
Prentice’s criterion four: Is treatment still prognostic for 5-year OS in patients stratified by the surrogate?
 Patients with failure or death from any cause ≤ 3 years
  Yes NS >0.10
  No NS >0.10
 Patients with failure at any site ≤ 3 years
  Yes NS >0.10
  No NS >0.10
 Patients with distant metastasis ≤ 3 years
  Yes NS >0.10
  No NS >0.10
  1. Abbreviations: CI confidence interval; HR hazard ratio; NS not significant; OS overall survival
  2. aAs treatment was not prognostic for any surrogates measured at 2 years and locoregional failure at 3 years, Prentice’s criterion three and four were not tested for these endpoints
  3. bThe reference groups were no events ≤ 3 years
  4. cHazard ratios were adjusted for the following parameters using a Cox proportional hazards model by backward elimination: age (>50 vs. ≤ 50 years), gender (male vs. female), T category (T3–4 vs. T1–2), N category (N1–3 vs. N0), surrogates (with vs. without events ≤ 3 years) for Prentice’s criterion three only, and treatment arm (neoadjuvant chemotherapy + concurrent chemoradiotherapy vs. concurrent chemoradiotherapy) for Prentice’s criterion four only
  5. *P-values were calculated using the adjusted Cox proportional hazards model